What are the options for extending a 30-day visa in Bangkok?

Just called for an appointment and was told its 2800b. And clarified that the service fee is 900b..!

Lets see on Saturday

Other than Chaengwattana there is no official immigration office that will do 30 day extensions on 30 day visa exempt or 60 day tourist visas.

Bumrungrad hospital has a service where an immigration officer comes there on Saturday from 9-11 and does 30 day extensions for the 1900baht plus an 800 baht service charge.

You should call and put your name on the list, because people who just showed up were told to do so next time or they couldn't get an extension.

What you will need at any immigration to get your extension

You have to phone to make a appointment and its the usual 1900 bt + 800 saturdays only i believe